The mortality of acute renal failure (ARF) remains to be high (around 60-70%) despite manifold improvements in ICU care. At present, it is not clear if the method chosen for renal replacement therapy, i.e. intermittent haemodialysis (IHD) or continuous haemofiltration (CVVH), might impact on the outcome of these patients. For this purpose, a prospective randomised clinical study of the effect of continuous versus intermittent renal replacement therapy on the mortality and outcome of acute renal failure will be performed.